The Del Air Rockhounds Club, Inc
Los Angeles - San Fernando Valley, California, United States
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Wednesday, January 6, 2010

January 2010 Mineral of the Month

SULFUR

Named from the Middle English word 'sulphur' meaning brimstone. Crystals are usually yellow to yellowish-brown blocky dipyramids with thick tabular and disphenodal crystals being less common. Native sulfur is usually formed from volcanic action as a sublimate from volcanic gasses associated with realgar, cinnabar, and other minerals. It is also found in some vein deposits and as an alteration product of sulfide minerals. It can also be formed biogenically, a major source being salt domes, where it has formed by the bacterial decomposition of calcium sulfate.

Sulfur is a member of the native elements group and has a hardness of 1-1/2 to 2-1/2 on the Mohs Scale. Its specific gravity is 2.0 to 2 .1. Sulfur has a resinous luster and an imperfect cleavage with an uneven to conchoidal fracture. Its chemical composition is S

Sulfur fuses at the relatively low temperature of 113 degrees and gives off choking fumes of sulfur dioxide when burned. There are many industrial uses of sulfur ranging from matches and fireworks to rubber.